First, the music thing has little to do with honour your mother. We’re discussing the music and how appropriate it is. I am not advising the OP to be disobedient or disrespectful so I’m not sure why you see the false dichotomy there.
When his mother says “I want you to participate in this group” about which we know nothing, and we tell the kid to tell his mom to shove off, what we’re discussing is PRECISELY honoring one’s father and mother.
WE don’t know anything about the group. WE don’t know anything about the music they present other than a couple of vague terms the OP discussed. WE have no insight as to why the mother made this request, and no way of knowing that it is an invalid request.
So
how dare we tell this child not to honor his mother?
Secondly, it works both ways with regards to the “We haven’t heard exactly what is being played”. Yes, we haven’t, and so we’re going by what we know. Should we give the benefit of the doubt? Well…
No, we’re going by what the OP, who admittedly has some bias because he doesn’t want to join this group, has told us. We’re not getting the full story here, while the Mom is. This is no different than the people who come and complain about their priest and his abuses, only to find out that the “fruity hippy poem” was the pentecost prayer that has been universal for 500+ years (and yes, that was what someone called it and there were several posters telling the OP to write the bishop before someone pointed out that the OP bias shouldn’t be followed).
It’s a tendency on a forum to regard OPs with sympathy and view their quite obviously emotive posts as objective truth. I’m saying that in this case, the mother knows the situation better than any of us and we have no right to contradict her where we know less.
No. Folksy music with guitars has no place in the Mass. Ever. That is not just my personal opinion either, if it weren’t just about my bedtime I’d find the document which says we must avoid bringing the secular into the Mass. Also, see above. This group wants to make Mass “fun”. How utterly offensive to our Lord, and to the youth involved.
Guitars are no more “secular” than pianos and violins. I agree that the profane should not be introduced, but the presence of a guitar or a drum does not necessarily make something profane.
As to folk music, as I pointed out above, gregorian chant is technically folk music, and I’m fairly certain you wouldn’t deny that gregorian chant has a place in the mass.
As to making the mass fun and engaging, I don’t have any problem with that, nor does the vatican. We are not to regard the mass as a “dreadfully boring time but something we have to do in order to please God.” There are, again, a lot of definitions of “fun”.